As the popularity of electric vehicles as alternatives to gas-powered vehicles increases in the United States and elsewhere, there is a growing need for plastics that can be used as wire and plug covers for electric vehicle recharging units. Some of these electric vehicle charging units are stationary, while others are portable. So-called electric vehicle supply equipment having a cord connector conveniently enables charging of electric vehicle batteries. The plastics that are used in these units must meet various safety standards relating to flame retardance and thermal stability. These standards include UL94 V-0, the glow wire flammability test, and the ball pressure test.
UL94 is the most rigorous plastics flammability vertical standard from Underwriters Laboratories (USA). A “V-0” rating according to UL 94 means that a vertical plastic sample that has been ignited by a flame stops burning within 10 seconds. The total flaming combustion time of the sample cannot exceed 50 seconds, and ignited samples cannot drip flaming particles. Finally, the ignited sample cannot have glowing combustion more than 30 seconds after the flame is removed.
The glow wire flammability test is used to simulate the heat that may result from a malfunctioning electrical device, such as electrically overloaded or glowing components. The test offers a way to compare the ability of various materials to extinguish flames and to compare their propensity to produce particles capable of spreading fire. In the test, a sample is held against a glowing wire for 30 seconds. The glow wire is removed, and the time for the flames to extinguish is recorded. The glow wire flammability index is the highest temperature where there is no flame or glowing (no ignition) and/or glowing time is less than 30 seconds.
The ball pressure test is used to determine dimensional stability under stress at elevated temperature. It is used to test the performance of plastic insulating materials that are used in electrical appliances, wiring accessories, lights, motors, connectors, and so on. The test is designed to evaluate heat resistance in order to ensure that the external parts of the insulating material do not excessively soften when heated.
Moreover, there is also a demand for plastics that are more environmentally friendly and thus that are halogen-free. As a result, there is an ongoing need for flame retardant, non-halogenated plastic materials that can be used in a range of products, including as coverings for electric wires and plugs.